Cutting tools employing a resilient clamping mechanism for clamping cutting inserts are generally of relatively narrow thickness. For example, cutting operations such as grooving and parting off can be performed by a cutting insert retained in an insert pocket located between the clamping surfaces of upper and lower jaws of a relatively narrow holder blade. The holder blade is, in turn, generally clamped in a blade-retaining block. The holder blade is generally provided with a suitably designed opening, in the vicinity of the insert pocket whereby a relatively narrow bridging portion is formed enabling a limited degree of resilient displacement of one of the holder blade's jaws relative to the other. Generally, the lower jaw is rigid and the upper jaw is resiliently displaceable. The opening can be of the form of an aperture,or a slot, or a slot terminating in an aperture. Examples of such cutting tools are disclosed in U.S. Pat. No 3,785,021 and U.S. Pat. No 4,580,930. A rotary slot-cutting tool employing a resilient insert clamping mechanism is disclosed in U.S. Pat. No 5,059,068. The cutter body is disc-shaped and of relatively narrow thickness, with cutting insert pockets located around its periphery. As with the holder blade, an insert pocket of a rotary slot-cutting tool has two jaws between which an insert is clamped by means of the resilient force resulting from the bending of the clamping jaw.
Whether the cutting tool is a holder blade or a rotary slot cutting tool, the bending of the clamping jaw is obtained by manufacturing the insert pocket such that the distance between the clamping surfaces of the jaws is smaller than the height of the portion of the insert located between the clamping surfaces. Consequently, when an insert is located in the insert pocket, the clamping jaw is held in a bent position creating an elastic force by means of which the insert is clamped in position.
An example of a well-known problem with cutting tools of the type described above is that a forward region of the insert pocket can come into contact with the workpiece and consequently become damaged. This can be particularly problematic with rotary slot cutting tools, where the damaging of one or two insert pockets requires the replacing of the whole cutting tool. A solution to this problem is proposed in U.S. Pat. No. 4,604,004 in which there is disclosed a cutting tool assembly having a hard, wear resistant insert, a shim and a blade body. The shim has a recess that tapers towards its open end to springingly hold the insert. The blade body has a downwardly and rearwardly extending recess that tapers toward the blade body to wedgingly hold the shim and insert. Assembly of the cutting tool assembly is accomplished by first inserting the insert into the shim recess, after which the shim, with the insert mounted therein, is inserted into the blade body recess. As the cutting tool assembly is contacted with a workpiece, the insert and the shim are wedged further into the blade body recess, thereby increasing the positive retention of the insert and the shim. After a period of use, the insert and shim are removed from the body so that the insert can be replaced. The shim is removed from the blade body by inserting a screwdriver in a gap between the blade body and the shim and applying a prying action to the screwdriver. The insert is removed from the shim by inserting a screwdriver into a notch of the shim and then twisting the screwdriver.
A disadvantage of the cutting tool assembly disclosed in the '004 patent is that after assembling the cutting tool assembly, the cutting edge of the cutting insert is not precisely located. As pointed out in the '004 patent, the insert and the shim are further wedged into the blade body recess as the cutting tool assembly is contacted with a workpiece. This situation is particularly disadvantageous for rotary slot cutting tools where there are a plurality of cutting inserts spaced about the periphery of the tool and imprecise location of the cutting edges of the cutting inserts results in inefficient cutting operations in which some of the inserts participate more in the cutting operation than others.
In the '004 Patent the member in which the cutting insert is mounted is referred to as a "shim". In the following description and claims the member in which the cutting insert is mounted will be referred to as an "insert retention member".
It is an object of the present invention to provide a cutting tool assembly having a replaceable insert retention member with a resilient clamping mechanism that does not suffer from the above mentioned disadvantage.
A further disadvantage of the cutting tool assembly disclosed in the '004 patent is that in order to remove a retained cutting insert, the shim has to be removed from the blade body recess. It is a further object of the present invention to provide an embodiment of a cutting tool assembly having a replaceable insert retention member with a resilient clamping mechanism that does not require the removal of the insert retention member in order to remove a retained cutting insert.
A yet further disadvantage of the cutting tool assembly disclosed in the '004 patent is that, the shim is not secured to the blade body. This can be especially problematic if the shim is used in a rotary slot-cutting tool, since there is nothing to prevent the shim from becoming displaced during a slotting operation. It is yet a further object of the present invention to provide an embodiment of a cutting tool assembly having a replaceable insert retention member with a resilient clamping mechanism that is firmly secured to the body of the rotary slot cutting tool.